A human case of swine influenza virus infection in Europe--implications for human health and research. Euro Surveill. 2009 Feb 19;14(7). pii: 19124.

Swine are susceptible to the same influenza A virus subtypes as humans--H1N1, H3N2 and H1N2--and the histories of influenza in pigs and people are closely linked. Many swine influenza viruses are a result of reassortment and their genes are composed of human and avian and/or swine virus genes. Indeed, it is known that both human and avian influenza viruses occasionally transmit to pigs, and that pigs can serve as "mixing vessels" for these viruses, meaning that viruses can exchange genetic material and lead to the production of a new "hybrid" virus. This has led to the thinking that perhaps pandemic viruses could emerge following reassortment in pigs. However, since nobody has observed the start of a pandemic, there remains no direct evidence to make this more than a theory.

Update: swine influenza A (H1N1) infections--California and Texas, April 2009.

On April 21, 2009, CDC reported that two recent cases of febrile respiratory illness in children in southern California had been caused by infection with genetically similar swine influenza A (H1N1) viruses. The viruses contained a unique combination of gene segments that had not been reported previously among swine or human influenza viruses in the United States or elsewhere. Neither child had known contact with pigs, resulting in concern that human-to-human transmission might have occurred. The seasonal influenza vaccine H1N1 strain is thought to be unlikely to provide protection. This report updates the status of the ongoing investigation and provides preliminary details about six additional persons infected by the same strain of swine influenza A (H1N1) virus identified in the previous cases, as of April 24. The six additional cases were reported in San Diego County, California (three cases), Imperial County, California (one case), and Guadalupe County, Texas (two cases). CDC, the California Department of Public Health, and the Texas Department of Health and Human Services are conducting case investigations, monitoring for illness in contacts of the eight patients, and enhancing surveillance to determine the extent of spread of the virus. CDC continues to recommend that any influenza A viruses that cannot be subtyped be sent promptly for testing to CDC. In addition, swine influenza A (H1N1) viruses of the same strain as those in the U.S. patients have been confirmed by CDC among specimens from patients in Mexico. Clinicians should consider swine influenza as well as seasonal influenza virus infections in the differential diagnosis for patients who have febrile respiratory illness and who 1) live in San Diego and Imperial counties, California, or Guadalupe County, Texas, or traveled to these counties or 2) who traveled recently to Mexico or were in contact with persons who had febrile respiratory illness and were in one of the three U.S. counties or Mexico during the 7 days preceding their illness onset.

Experimental infection of pigs with the human 1918 pandemic influenza virus.J Virol. 2009 May;83(9):4287-96. Epub 2009 Feb 18.

Swine influenza was first recognized as a disease entity during the 1918 "Spanish flu" pandemic. The aim of this work was to determine the virulence of a plasmid-derived human 1918 pandemic H1N1 influenza virus (reconstructed 1918, or 1918/rec, virus) in swine using a plasmid-derived A/swine/Iowa/15/1930 H1N1 virus (1930/rec virus), representing the first isolated influenza virus, as a reference. Four-week-old piglets were inoculated intratracheally with either the 1930/rec or the 1918/rec virus or intranasally with the 1918/rec virus. A transient increase in temperature and mild respiratory signs developed postinoculation in all virus-inoculated groups. In contrast to other mammalian hosts (mice, ferrets, and macaques) where infection with the 1918/rec virus was lethal, the pigs did not develop severe respiratory distress or become moribund. Virus titers in the lower respiratory tract as well as macro- and microscopic lesions at 3 and 5 days postinfection (dpi) were comparable between the 1930/rec and 1918/rec virus-inoculated animals. In contrast to the 1930/rec virus-infected animals, at 7 dpi prominent lung lesions were present in only the 1918/rec virus-infected animals, and all the piglets developed antibodies at 7 dpi. Presented data support the hypothesis that the 1918 pandemic influenza virus was able to infect and replicate in swine, causing a respiratory disease, and that the virus was likely introduced into the pig population during the 1918 pandemic, resulting in the current lineage of the classical H1N1 swine influenza viruses.

Update: drug susceptibility of swine-origin influenza A (H1N1) viruses, April 2009.MMWR Morb Mortal Wkly Rep. 2009 May 1;58(16):433-5.

Since April 21, 2009, CDC has reported cases of respiratory infection with a swine-origin influenza A (H1N1) virus (S-OIV) that is being spread via human-to-human transmission. As of April 28, the total number of confirmed S-OIV cases in the United States was 64; these cases occurred in California (10 cases), Kansas (two), New York (45), Ohio (one), and Texas (six). The viruses contain a unique combination of gene segments that had not been reported previously among swine or human influenza viruses in the United States or elsewhere. Viruses from 13 (20%) of 64 patients have been tested for resistance to antiviral medications. To date, all tested viruses are resistant to amantadine and rimantadine but are susceptible to oseltamivir and zanamivir. The purpose of this report is to provide detailed information on the drug susceptibility of the newly detected S-OIVs, which will aid in making recommendations for treatment and prophylaxis for swine influenza A (H1N1) infection. These data also will contribute to antiviral-resistance monitoring and diagnostic test development.

Update: infections with a swine-origin influenza A (H1N1) virus--United States and other countries, April 28, 2009.MMWR Morb Mortal Wkly Rep. 2009 May 1;58(16):431-3.

Since April 21, 2009, CDC has reported cases of respiratory infection with a swine-origin influenza A (H1N1) virus (S-OIV) transmitted through human-to-human contact. This report updates cases identified in U.S. states and highlights certain control measures taken by CDC. As of April 28, the total number of confirmed cases of S-OIV infection in the United States had increased to 64, with cases in California (10 cases), Kansas (two), New York (45), Ohio (one), and Texas (six). CDC and state and local health departments are investigating all reported U.S. cases to ascertain the clinical features and epidemiologic characteristics. On April 27, CDC distributed an updated case definition for infection with S-OIV.

Further evidence for infection of pigs with human-like H1N1 influenza viruses in China.Virus Res. 2009 Mar;140(1-2):85-90. Epub 2009 Jan 3.

Classical swine and avian-like H1N1 influenza viruses were reported widely in swine population worldwide, but human-like H1N1 swine viruses were reported occasionally. In 2006, a human-like H1N1 swine virus (A/swine/Guangdong/96/06) was isolated from pigs in Guangdong province, which was reported in China for the first time. To get further evidence for infection of pigs with human-like H1N1 influenza viruses, we analyzed eight gene segments of three human-like swine H1N1 viruses (A/swine/Guangdong/96/06, A/swine/Tianjin/01/04 and A/swine/Henan/01/06) isolated in China. All the eight genes of the three viruses are highly homologous to recent (about 2000) and early (1980s) human H1N1 influenza viruses, respectively. Phylogenetic analyses revealed that A/Swine/Guangdong/96/06 was directly derived from about 2000 human H1N1 influenza viruses, while A/swine/Tianjin/01/04 and A/swine/Henan/01/06 seemed to be descendants of human H1N1 viruses circulating in 1980s. Seroprevalence of our isolate (A/swine/Guangdong/96/06) confirmed the presence of human-like H1N1 virus in pigs in China. Existence of these influenza viruses, especially older viruses (A/swine/Tianjin/01/04 and A/swine/Henan/01/06), indicates that human-like H1N1 influenza viruses may remain invariant for long periods in pigs and provides the evidence that pigs serve as reservoirs of older influenza viruses for human pandemics.

( Tuesday May 5, 2009:  India continues to be free from swine flu infection, while five passengers with suspected influenza A (H1N1) symptoms are quarantined.)

With the World Health Organisation designating swine influenza outbreak as a public health emergency of international concern, India on Monday ( 27th April 2009) put on alert all international airports and ports for identifying persons with suspected infection who could be arriving from countries affected.

Those travelling to affected areas have also been advised to defer non-essential journeys. Instructions were issued to track down people who arrived in India from Mexico, the U.S., Canada, New Zealand, Spain, France and the United Kingdom.

Keeping in view the global scenario, the government is instituting a series of preventive action that includes surveillance at ports and international airports.  All passengers coming to India from the affected areas will be mandatorily screened for influenza symptoms while for others it will be voluntary.

The 21 airports in the country where screening is being done are: Ahmedabad, Amritsar, Bangalore, Calicut, Chennai, Cochin, Coimbatore, New Delhi, Varanasi, Goa, Hyderabad, Jaipur, Kolkata, Lucknow, Mangalore, Mumbai, Nagpur, Pune, Srinagar, Tiruchirapalli and Tiruvananthapuram.

Four labs - National Institute of Communicable Diseases (NICD) in Delhi. National Institute of Virology (Pune), National Institute of Cholera and Enteric Diseases (Kolkata) and Regional Medical Research Centre (Dibrugarh) - have been put on high alert to test human samples for H1N1 infection.

Doctors clarified that there is no risk of the flu from eating pork and pork products, including ham, salami and sausages. Otherwise, it is advised that pork be cooked at temperatures over 70 degrees - a level at which all viruses die.

The new flu does not have any preventive vaccine for humans, although timely  medication  can cure it. The medicine advised is Tamiflu and Relenza.